Loss Circulation Material Composition Having Alkaline Nanoparticle Based Dispersion and Water Insoluble Hydrolysable Polyester

ABSTRACT

A lost circulation material (LCM) is provided having an alkaline nanosilica dispersion and a polyester activator. The alkaline nanosilica dispersion and the polyester activator may form a gelled solid after interaction over a contact period. Methods of lost circulation control using the LCM are also provided.

BACKGROUND Field of the Disclosure

The present disclosure generally relates to controlling lost circulationin a well during drilling with a drilling fluid. More specifically,embodiments of the disclosure relate to lost circulation materials(LCMs).

Description of the Related Art

Various challenges are encountered during drilling and productionoperations of oil and gas wells. For example, fluids used in drilling,completion, or servicing of a wellbore can be lost to the subterraneanformation while circulating the fluids in the wellbore. In particular,the fluids may enter the subterranean formation via depleted zones,zones of relatively low pressure, lost circulation zones havingnaturally occurring fractures, weak zones having fracture gradientsexceeded by the hydrostatic pressure of the drilling fluid, and soforth. The extent of fluid losses to the formation may range from minorlosses (for example less than 10 barrels/hour ((bbl/hr), also referredto as seepage loss, to severe (for example, greater than 100 bbl/hr), orhigher, also referred to referred to as complete fluid loss. As aresult, the service provided by such fluid is more difficult or costlyto achieve.

Such lost circulation can be encountered during any stage of operationsand occurs when drilling fluid (or drilling mud) pumped into a wellreturns partially or does not return to the surface. While de minimisfluid loss is expected, excessive fluid loss is not desirable from asafety, an economical, or an environmental point of view. Lostcirculation is associated with problems with well control, boreholeinstability, pipe sticking, unsuccessful production tests, poorhydrocarbon production after well completion, and formation damage dueto plugging of pores and pore throats by mud particles. Lost circulationproblems may also contribute to non-productive time (NPT) for a drillingoperation. In extreme cases, lost circulation problems may forceabandonment of a well.

SUMMARY

Lost circulation materials (LCMs) are used to mitigate lost circulationby blocking the path of the drilling mud into the formation. The type ofLCM used in a lost circulation situation depends on the extent of lostcirculation and the type of formation. Existing LCMs may perform poorlyin mitigation and prevention of moderate lost circulation and seepagetype lost circulation, and may not be suitable for controlling severeloss of circulation. Costs incurred in loss circulation situations maybe due to losses of drilling fluids, losses of production, and the costsof LCMs.

In one embodiment, a method to control lost circulation in a lostcirculation zone in a wellbore is provided. The method includesintroducing a lost circulation material (LCM) into the wellbore suchthat the LCM contacts the lost circulation zone and reduces a rate oflost circulation into the lost circulation zone as compared to a periodbefore introducing the LCM. The LCM includes an alkaline nanosilicadispersion and a water insoluble polyester. In some embodiments, whereinthe LCM consists of the alkaline nanosilica dispersion and the waterinsoluble polyester. In some embodiments, the water insoluble polyesterincludes at least one of a polylactide, a polyhydroxyalkanoate,polyglycolide, polylactoglycolide, and polycaprolactone. In someembodiments, the water insoluble polyester is in an amount in the rangeof 0.1 percent by volume of the total volume (v/v %) to 10 v/v %. Insome embodiments, the method includes maintaining the alkalinenanosilica dispersion and water insoluble polyester in contact with thelost circulation zone for a contact period, such that the alkalinenanosilica dispersion forms a gelled solid. In some embodiments, thecontact period is a range of 0.5 hours to 24 hours. In some embodiments,the lost circulation zone has a temperature that is at least 100° F. Insome embodiments, the method includes mixing the alkaline nanosilicadispersion and the water insoluble polyester to form the LCM at thesurface before introducing the LCM into the wellbore. In someembodiments, the LCM includes at least one of calcium carbonateparticles, fibers, mica, and graphite. In some embodiments, the fibersinclude at least one of polyester fibers, polypropylene fibers, starchfibers, polyketone fibers, ceramic fibers, glass fibers and nylonfibers.

In one embodiment, a lost circulation material (LCM) compositionincludes an alkaline nanosilica dispersion and a water insolublepolyester, the water insoluble polyester selected to form a gelled solidwith the alkaline nanosilica dispersion after a period. In someembodiments, the period is a range of 0.5 hours to 24 hours. In someembodiments, the water insoluble polyester includes at least one of apolylactide, a polyhydroxyalkanoate, polyglycolide, polylactoglycolide,and polycaprolactone. In some embodiments, the water insoluble polyesterincludes an amount in the range of 0.1 percent by volume of the totalvolume (v/v %) to 10 v/v %.

In another embodiment, a solid gelled material useful for mitigatinglost circulation is provided. The solid gelled material forms byintroducing an alkaline nanosilica dispersion and a water insolublepolyester to a lost circulation zone. The nanosilica dispersion includesamorphous silicon dioxide and water, such that the nanosilica dispersionand the water insoluble polyester contact the lost circulation zone fora period such that the solid gelled material forms. In some embodiments,the water insoluble polyester includes at least one of a polylactide, apolyhydroxyalkanoate, polyglycolide, polylactoglycolide, andpolycaprolactone. In some embodiments, the water insoluble polyesterincludes an amount in the range of 0.1 percent by volume of the totalvolume (v/v %) to 10 v/v %. In some embodiments, the water insolublepolyester is introduced separately from the alkaline nanosilicadispersion to the lost circulation zone. In some embodiments, the waterinsoluble polyester and the alkaline nanosilica dispersion areintroduced simultaneously to the lost circulation zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of the solid formed by a mixture of an alkalinenanosilica dispersion with s polylactide activator; and

FIG. 2 is a photograph of the solid formed by a mixture of an alkalinenanosilica dispersion with s polylactide activator.

DETAILED DESCRIPTION

The present disclosure will be described more fully with reference tothe accompanying drawings, which illustrate embodiments of thedisclosure. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art.

Embodiments of the disclosure include a lost circulation material (LCM)that includes an alkaline nanosilica dispersion and a water insolublehydrolysable polyester activator. The LCM may mitigate or prevent lostcirculation in a well, as well as provide seepage control and minimizeor prevent fluid loss. In some embodiments, the polyester activator maybe polylactide. In other embodiments, the polyester activator mayinclude polyhydroxyalkanoates, polyglycolide, polylactoglycolide, andpolycaprolactone. The alkaline nanosilica dispersion may have a pH of atleast 8, such as in the range of about 8.5 to about 10.5 beforeinteraction with the polyester activator. The alkaline nanosilicadispersion and polyester activator LCM may be introduced into a lostcirculation zone in a wellbore, such that the alkaline nanosilicadispersion and polyester activator LCM alters the lost circulation zone.The alkaline nanosilica dispersion and polyester activator LCM may beallowed to interact with the lost circulation zone for a time period toenable the in-situ formation of a gelled solid as a result of theinteraction between the alkaline nanosilica dispersion and an acidgenerated from the polyester activator via hydrolysis.

Alkaline Nanosilica Dispersion and Polyester Activator LCM

In some embodiments, an LCM includes an alkaline nanosilica dispersionand a water insoluble hydrolysable polyester activator. The alkalinenanosilica dispersion may include amorphous silicon dioxide and anaqueous medium. For example, in some embodiments, the alkalinenanosilica dispersion may be formed using water or other suitableaqueous mediums (for example, water and glycerin). In some embodiments,the nanosilica dispersion has a pH of about 8.5 to about 10.5 at 25° C.before interaction with the polyester activator. In some embodiments,the nanosilica dispersion has a pH of at least 8 before interaction withthe activator. In some embodiments, the nanosilica dispersion has aspecific gravity of 1.2 (g/ml). In some embodiments, the nanosilicadispersion may be obtained from Evonik Corporation of Parsippany, N.J.,USA.

In some embodiments, the water insoluble hydrolysable polyesteractivator may include polylactide. In other embodiments, the polyesteractivator may include other water insoluble hydrolysable polyesters,such as polyhydroxyalkanoates, polyglycolide, polylactoglycolide, andpolycaprolactone. In some embodiments, the weight ratio of the alkalinenanosilica dispersion to the polyester activator is in the range of 50:1to 80:1. For example, in some embodiments, the weight ratio of thealkaline nanosilica dispersion to the polyester activator is 66:1. Insome embodiments, the polyester activator may be in an amount in therange of about 0.1 percent by volume of the total volume (v/v %) toabout 10 v/v %

In some embodiments, the nanosilica dispersion and polyester activatorLCM may include additional materials. For example, in some embodimentthe nanosilica dispersion and polyester activator LCM may includecalcium carbonate particles, fibers (for example, polyester fibers,polypropylene fibers, starch fibers, polyketone fibers, ceramic fibers,glass fibers nylon fibers, or combinations thereof), mica, graphite, orcombinations thereof.

The alkaline nanosilica dispersion and polyester activator LCM may beintroduced (for example, by pumping) into a lost circulation zone in awellbore to control lost circulation. In some embodiments, the alkalinenanosilica dispersion and polyester activator LCM may be allowed tointeract with the lost circulation zone for a contact period. Thecontact period may be of sufficient duration to enable formation of asolid as a result of the interaction between the alkaline nanosilicadispersion and the polyester activator. The formed solid may alter thelost circulation zone (for example, by entering and blocking porous andpermeable paths, cracks, and fractures in a formation in the lostcirculation zone, such as forming a structure in a mouth or within afracture). In some embodiments, the polyester and the alkalinenanosilica dispersion may be introduced simultaneously to the lostcirculation zone. In other embodiments, the polyester activator may beintroduced separately from the alkaline nanosilica dispersion to thelost circulation zone.

In some embodiments, the contact period may be in the range of about 0.5hours to about 24 hours. For example, in some embodiments the contactperiod may be about 16 hours. In some embodiments, the contact periodmay be selected based on the formation type of the lost circulationzone.

As shown infra, the alkaline nanosilica dispersion and polyesteractivator may form a solid LCM after a sufficient time period. In someembodiments, the gelling of the alkaline nanosilica dispersion may becontrolled by varying the concentration of the polyester activator, andthe gelling may be controlled by changing the pH of the LCM. Forexample, increasing concentrations of the polyester activator mayincrease the pH of the LCM and increase the rate of gelation of the LCM.Additionally, the polyester activator exhibits no precipitation with thealkaline nanosilica dispersion at elevated temperature, thus enablinguse of the LCM composition as a single fluid pill (that is, withoutstaged mixing of each component). Consequently, the delayed andcontrolled gelling of the alkaline nanosilica dispersion LCM may providefor easier pumping of the LCM. The alkaline nanosilica dispersion andpolyester activator LCM may be used at elevated temperatures in awellbore such as, for example, temperatures greater than 100° F., suchas 300° F. In some embodiments, the alkaline nanosilica dispersion andpolyester activator LCM may be used in lost circulation zones havingtemperatures below 100° F. In such embodiments, the LCM may include acatalyst to increase the rate of hydrolysis of the ester. In someembodiments, the catalyst may include hydrochloric acid, sulfuric acid,or other suitable acids. Moreover, the environmentally friendlyproperties of the alkaline nanosilica dispersion and polyester activatorLCM may minimize or prevent any environmental impact and effect onecosystems, habitats, population, crops, and plants at or surroundingthe drilling site where the alkaline nanosilica dispersion and polyesteractivator LCM is used.

EXAMPLES

The following examples are included to demonstrate embodiments of thedisclosure. It should be appreciated by those of skill in the art thatthe techniques and compositions disclosed in the example which followsrepresents techniques and compositions discovered to function well inthe practice of the disclosure, and thus can be considered to constitutemodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or a similar result without departing from the spirit and scope ofthe disclosure.

The following non-limiting example of an alkaline nanosilica dispersionwas tested with a water insoluble hydrolysable polyester activator.

The alkaline nanosilica dispersion used was IDISIL® SI 4545 manufacturedby Evonik Corporation of Parsippany, N.J., USA. The properties of thenanosilica dispersion are described in Table 1:

TABLE 1 Properties of Alkaline Nanosilica Dispersion Nanosilicadispersion pH @ 25° C. 8.5-10.5 Specific Gravity (grams/milliliter(g/ml))   1.2 Viscosity @ 25° C. (cP) <30  Visual Appearance White/OffWhite Weight % SiO2 45

A composition was prepared using the alkaline nanosilica dispersion andpolylactide. 100 milliliters (ml) of the alkaline nanosilica dispersionwas added to an empty beaker. 2 grams (g) of polylactide (that is, 1gram of polylactide per 66 grams of alkaline nanosilica dispersion) wasadded to the alkaline nanosilica dispersion and mixed using a stirrer.The alkaline nanosilica dispersion-polylactide mixture was subjected tostatic aging in an aging cell. The cell was static aged at a temperatureof about 250° F. for about 16 hours to simulate downhole conditions.

After 16 hours of static aging, the alkaline nanosilica dispersion wasconverted into a solid. The polylactide hydrolyzed in the aqueous medium(for example, water) of the alkaline nanosilica dispersion to generate aresulting acid. The acid acted as an activator that destabilized thealkaline nanosilica dispersion and produced a solid. FIGS. 1 and 2 arephotographs 100 and 200 respectively of the solid formed by the mixtureof the alkaline nanosilica dispersion with the polylactide activator.The formation of the solid after static aging at the elevatedtemperature of 250° F. shows that the alkaline nanosilica dispersion canbehave as an LCM when introduced with a water insoluble hydrolysablepolyester activator.

Ranges may be expressed in the disclosure as from about one particularvalue, to about another particular value, or both. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value, to the other particular value, or both, along withall combinations within said range.

Further modifications and alternative embodiments of various aspects ofthe disclosure will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the embodiments described inthe disclosure. It is to be understood that the forms shown anddescribed in the disclosure are to be taken as examples of embodiments.Elements and materials may be substituted for those illustrated anddescribed in the disclosure, parts and processes may be reversed oromitted, and certain features may be utilized independently, all aswould be apparent to one skilled in the art after having the benefit ofthis description. Changes may be made in the elements described in thedisclosure without departing from the spirit and scope of the disclosureas described in the following claims. Headings used described in thedisclosure are for organizational purposes only and are not meant to beused to limit the scope of the description.

1. A method to control lost circulation in a lost circulation zone in awellbore, comprising: introducing a lost circulation material (LCM) intothe wellbore such that the LCM contacts the lost circulation zone andreduces a rate of lost circulation of a drilling fluid into the lostcirculation zone as compared to a period before introducing the LCM,wherein the LCM comprises an alkaline nanosilica dispersion and a waterinsoluble polyester, wherein the weight ratio of the alkaline nanosilicadispersion to the polyester activator is in the range of 50:1 to 80:1.2. The method of claim 1, wherein the LCM consists of the alkalinenanosilica dispersion and the water insoluble polyester.
 3. The methodof claim 1, wherein the water insoluble polyester comprises at least oneof a polylactide, a polyhydroxyalkanoate, polyglycolide,polylactoglycolide, and polycaprolactone.
 4. (canceled)
 5. The method ofclaim 1, comprising maintaining the alkaline nanosilica dispersion andwater insoluble polyester in contact with the lost circulation zone fora contact period, such that the alkaline nanosilica dispersion forms agelled solid.
 6. The method of claim 5, wherein the contact periodcomprises a range of 0.5 hours to 24 hours.
 7. The method of claim 1,wherein the lost circulation zone has a temperature that is at least100° F.
 8. The method of claim 1, comprising mixing the alkalinenanosilica dispersion and the water insoluble polyester to form the LCMat the surface before introducing the LCM into the wellbore.
 9. Themethod of claim 1, wherein the LCM comprises at least one of calciumcarbonate particles, fibers, mica, and graphite.
 10. The method of claim9, wherein the fibers comprises at least one of polyester fibers,polypropylene fibers, starch fibers, polyketone fibers, ceramic fibers,glass fibers and nylon fibers.
 11. The method of claim 1, wherein theLCM comprises a catalyst selected to increase an hydrolysis rate of thewater insoluble polyester.
 12. A lost circulation material (LCM)composition, comprising: an alkaline nanosilica dispersion; and a waterinsoluble polyester, the water insoluble polyester selected to form agelled solid with the alkaline nanosilica dispersion after a period. 13.The LCM composition of claim 12, wherein the period comprises a range of0.5 hours to 24 hours.
 14. The LCM composition of claim 12, wherein thewater insoluble polyester comprises at least one of a polylactide, apolyhydroxyalkanoate, polyglycolide, polylactoglycolide, andpolycaprolactone.
 15. The LCM composition of claim 12, wherein the waterinsoluble polyester comprises an amount in the range of 0.1 percent byvolume of the total volume (v/v %) to 10 v/v %.
 16. A solid gelledmaterial useful for mitigating lost circulation, where the solid gelledmaterial forms by introducing an alkaline nanosilica dispersion and awater insoluble polyester to a lost circulation zone, the nanosilicadispersion comprising amorphous silicon dioxide and water, such that thenanosilica dispersion and the water insoluble polyester contact the lostcirculation zone for a period such that the solid gelled material forms.17. The solid gelled material of claim 16, wherein the water insolublepolyester comprises at least one of a polylactide, apolyhydroxyalkanoate, polyglycolide, polylactoglycolide, andpolycaprolactone.
 18. The solid gelled material of claim 16, wherein thewater insoluble polyester comprises an amount in the range of 0.1percent by volume of the total volume (v/v %) to 10 v/v %.
 19. The solidgelled material of claim 16, wherein the water insoluble polyester isintroduced separately from the alkaline nanosilica dispersion to thelost circulation zone.
 20. The solid gelled material of claim 16,wherein the water insoluble polyester and the alkaline nanosilicadispersion are introduced simultaneously to the lost circulation zone.21. The method of claim 11, wherein the catalyst comprises hydrochloricacid or sulfuric acid.